I am in the planning process of building a completely mold resistant and healthy house to live in. For this, one would probably need to build with only non organic materials like glass, steel and plastics. This was the original intention. However, after investigating Styrene (a common plastic for insulation and an alternative to concrete) a bit more, it seems to be toxic to humans. Both harmful to the endocrine system as well as being carcinogenic. Then I researched concrete/cement, and this too seems to be toxic. So, what can you use? Steel by itself does not insulate enough. Stone perhaps?